N-(Arylthiocarbamoyl)-2-amino-1H-isoindole-1,3,-(2H) dione plant growth regulators

ABSTRACT

A novel class of compounds which are useful as plant growth regulators is disclosed, having the general structural formula: ##STR1## in which R 1  is: C 1  to C 4  alkyl, nitro or halo and n is zero or an integer from 1 to 4 
     R 2  and R 3  are: H or C 1  to C 4  alkyl, or benzyl and 
     Ar is: adamantyl, C 3  to C 4  alkyl or alkenyl, benzyl, halobenzyl, naphthyl, phenyl or phenyl bearing thereon from one to three of the substituents: cyano, benzyloxy, nitro, bromo, chloro, trifluoromethyl and C 1  to C 4  alkyl, alkenyl, alkoxy, alkylthio and alkyl-substituted amino.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 113,861 filed Feb. 5, 1980, now U.S. Pat. No. 4,264,502, which is a continuation-in-part of U.S. patent application Ser. No. 19,065, filed Mar. 9, 1979, abandoned.

DESCRIPTION OF THE INVENTION

Growth regulating effects have been observed upon application of many chemical substances to plants. In general, very few of these substances can be used with benefit to the plants which are affected. In most instances the beneficial effects, if any, are minor and the major effects are so drastic that the compounds can only be used for the destruction of the plants. Examples of growth regulator compounds with drastic effects which have become useful as herbicides are 2,4-D, EPTC and alachlor. Among the potential commercial uses for growth regulator compounds with less drastic effects are the following:

Increase or induce flowering (pineapple).

Increase blossom set, pod set, seed set, and/or fruit set (prevent abortion of flowers or withered blossoms).

Increase size of fruits, vegetables, seed, and/or tubers (grapes, soybeans, sugar beets, etc).

Decrease size of fruit, vegetables, seed, and/or tubers (potatoes, and grapefruits).

Increase number of tillers (cereals).

Increase number of shoots from crown (alfalfa).

Increase branching (soybeans) or widen branches (apples).

Reduce height (shortened internodes) in crops and ornamentals (cereals and mums).

Growth retardant (turf, cotton, perennial legumes in no-till corn).

Enhance yields of corn by larger ears, better filled ears and/or more ears per plant.

Increase nutritive value of seeds, fruits, vegetables, forages, etc. (protein content).

Reduce transpiration (drought resistance).

Reduce respiration (potatoes or sugar beets in storage).

We have discovered a group of novel compounds which display a great variety of growth regulating effects, indicating utility for many purposes, including uses mentioned above. The present invention is directed to these novel compounds, including methods of manufacture, as well as methods and formulations for plant growth regulation.

Briefly, the novel class of growth regulator compounds has the general structural formula: ##STR2## in which R¹ is: C₁ to C₄ alkyl, nitro or halo and n is zero or an integer from 1 to 4

R² and R³ are: H or C₁ to C₄ alkyl, or benzyl and

Ar is: adamantyl, C₃ to C₄ alkyl or alkenyl, benzyl, halobenzyl, naphthyl, phenyl or phenyl bearing thereon from one to three of the substituents: cyano, benzyloxy, nitro, bromo, chloro, trifluoromethyl and C₁ to C₄ alkyl, alkenyl, alkoxy, alkylthio and alkyl-substituted amino.

The aforementioned compounds are employed to regulate the growth of plants by applying an effective amount to the plants, the seed or the soil, preferably in combination with an inert carrier or diluent and a surface active agent, according to customary practice in the art.

SYNTHESIS OF THE GROWTH REGULATORS

The novel compounds of this invention may be produced from commercially available raw materials by means of procedures based on those outlined and specifically illustrated below:

The synthesis of N-(phenylthiocarbamoyl or substituted phenylthiocarbamoyl)-2-amino-1H-isoindole-1,3-(2H)dione (III), that is, the case of Structure I where R₁, R₂ and R₃ all are hydrogen, has been accomplished by reacting 2-amino-1H-isoindole-1,3-(2H)dione (II) with the corresponding aryl isothiocyanates. The preparation of starting material (II) was accomplished by the reaction of phthalimide with hydrazine in alcohol at <5° C. to give (II) in ˜70% yield with high purity. The literature procedure, J. Chem. Soc., 587 (1937), requires heating to reflux and gives a low (˜45%) yield. ##STR3## In the case of Structure (I) with n being equal to zero and R₂ being alkyl, special methods of preparation are required, as discussed below.

N-Methyl-N-(phenylthiocarbamoyl)-2-amino-1H-isoindole-1,3-(2H)-dione (IV) has been prepared by the cyclization of 2-(2-carboxybenzoyl)-1-methyl-N-phenylhydrazinethiocarboxamide with N,N'-dicyclohexylcarbodiimide, as outlined below: ##STR4##

According to two other schemes, the desired compounds were formed from intermediate compounds of the formula ##STR5## was obtained in a single step by reacting phthalic anhydride with N,1-dimethyl-N-phenylhydrazinethiocarboxamide (V) in chloroform. Similarly, commercially available ring substituted phthalic anhydrides and substituted 2-carbomethoxybenzoyl chlorides, made by conventional methods may be condensed with N-methyl and 1-methylhydrazinethiocarboxamides to give the corresponding specific compounds of formula (I), as in the following outline of synthesis procedures.

Below are specific illustrative procedures. The identity of the product was confirmed in each example by means of infrared and nuclear magnetic resonance spectra. All melting points are uncorrected.

2-Amino-1H-isoindole-1,3-(2H)dione (II)

To an ice-cold suspension of 14.7 g (0.1 mole) of phthalimide in 100 ml of 95% ethyl alcohol at 5° C., with stirring, 3.6 ml (0.11 mole) of 96.8% hydrazine was added dropwise. A slight exothermic reaction was observed and the mixture was allowed to stir at 5° C. for two hours. The mixture was diluted with 200 ml of ice water, stirred, filtered, washed with water and dried to give 12.2 g (75%) of white powder, m.p. 199°-202°.

Recrystallization from methanol-water gave white needles, m.p. 201°-203°.

N-(Phenylthiocarbamoyl)-2-amino-1H-isoindole-1,3-(2H)dione (III)

To a suspension of 8.2 g (0.05 mole) of II in 50 ml of dry 2-propanol, 6 ml (0.05 mole) of phenyl isothiocyanate was added. The mixture was stirred and refluxed for 3 hours, allowed to cool to room temperature and poured into 300 ml of 50% ethyl alcohol. After stirring for one hour, the solid which formed was filtered, washed with water and dried to give 12.1 g (81%) of the desired product as a white powder, m.p. 180°-181°.

N-Methyl-N-(phenylthiocarbamoyl)-2-amino-1H-isoindole-1,3-(2H)dione (IV)

Method 1

To an ice-cold solution of 8.25 g (0.025 mole) of 2-(2-carboxybenzoyl)-1-methyl-N-phenylhydrazinethiocarboxamide in 225 ml of 1,2-dimethoxyethane at ˜2° C., a solution of 5.5 g (0.027 mole) of N,N'-dicyclohexylcarbodiimide was added dropwise below 5° C. with stirring. The mixture was stirred in the ice bath and then left at room temperature overnight. The mixture was filtered to remove N,N'-dicyclohexylurea and the filtrate was evaporated below 40° C., under vacuum, to give a yellow amorphous solid which was stirred in 100 ml of dry ether and warmed gently. The ether solution was allowed to stand for a few hours and filtered to give 4.6 g (59%) of whitish yellow crystals, m.p. 142°-144°.

Recrystallization from ethyl acetate-hexane gave whitish crystals, m.p. 151°-153°.

Mass spectrum: M⁺ 311

Intermediate compounds of the type represented by the formula ##STR7## may be made by procedures of the type which are specifically illustrated below.

N,1-Dimethyl-N-phenylhydrazinethiocarboxamide (V)

To a solution of N-methyl-N-phenylthiocarbamyl chloride 79.6 g (0.43 m) in 250 ml dry ether, a solution of 39.5 g (0.86 m) methylhydrazine in 100 ml of dry ether was added dropwise with stirring below 10° C. The reaction temperature was allowed to increase to room temperature and filtered. The filtrate was evaporated to low volume and diluted with ˜300 ml hexane. After stirring for a few hours the hexane layer was decanted. The hexane immiscible layer was reevacuated to remove organic solvents, giving the desired product, 70.0 g as a thick orange liquid.

1-Methyl-N-phenylhydrazinethiocarboxamide (VII) is prepared by a procedure similar to the foregoing. The following procedure is illustrative of the preparation of an intermediate in which R² is H.

N-Methyl-N-phenylhydrazinethiocarboxamide

To a solution of 7.7 g (0.24 m) anhydrous hydrazine in 200 ml of dry ether, N-methyl-N-phenylthiocarbamyl chloride 20.4 g (0.11 m) was added below 5° C. with stirring. The mixture was stirred and allowed to warm to room temperature. The mixture was filtered and the residue resuspended in ˜100 ml water and stirred. Filtration gave 8.8 g of the desired product as whitish powder, m.p. 121°-22°.

The following procedures are illustrative of the use of the intermediates of the formula ##STR8##

N-Methyl-N-(phenylthiocarbamoyl)-2-amino-4-methyl-1H-isoindole-1,3-(2H)dione (VIII)

To a solution of 6.8 g (0.037 mole) of 1-methyl-N-phenylhydrazinethiocarboxamide (VII) and 3.0 g of pyridine in 100 ml dry dimethoxyethane, 2-carbomethoxy-6-methylbenzoyl chloride (8.0 g, 0.037 mole) was added and the resulting mixture was stirred at room temperature for 60 hours. The solvent was distilled and the residue was taken up in ethyl acetate, filtered and dried on anhydrous magnesium sulfate. Removal of the solvent gave 10 g (83%) of the desired product, m.p. 110°-115° (dec.).

N-Methyl-N-(phenyl-N-methylthiocarbamoyl)-2-amino-1H-isoindole-1,3-(2H)dione (VI)

To a slurry of 5.9 g (0.04 mole) of phthalic anhydride in 50 ml of dry chloroform, N,1-dimethyl-N-phenylhydrazinethiocarboxamide (7.8 g, 0.04 mole) (V) was added dropwise with stirring at room temperature to give an exothermic reaction. The mixture was stirred at room temperature overnight to give a clear solution. The solution was diluted with ˜250 ml of hexane to give an oily product. Decantation of the organic layer and extraction of the residue with 3×50 ml of anhydrous ether, filtration of the ether extracts and dilution with hexane precipitated the desired product. Filtration, washing with hexane and drying gave 8.6 g (66%) of solid, m.p. 175°-176°.

Use of the Growth Regulators

In highly active compounds, phytotoxic effects of pre-emergent and post-emergent application are often readily apparent. These effects may be demonstrated by means of the following illustrative procedures.

Pre-emergent Application

Disposable paper trays about 21/2 inches deep were filled with soil and sprayed with aqueous spray mixtures at a rate of 5 lb. of active chemical per acre of sprayed area, were seeded with 6 species of plant seeds and were then covered with about 1/4 inch of soil. The spray mixtures were prepared by dissolving the proper amount of growth regulator compound in 15 ml of acetone, adding 4 ml of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor EL-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 60 ml by addition of warm water. Twenty-one days after seeding and treatment the plantings were examined and plant injury was rated according to the following schedule:

    ______________________________________                                         DEGREE OF EFFECT                                                               ______________________________________                                         0 =      no effect                                                             1 =      slight effect, plants recovered                                       2 =      moderate effect, injury to 26 to 75 percent                           3 =      severe effect, injury to 76 to 99 percent                                      of foliage                                                            4 =      maximum effect (all plants died)                                      ______________________________________                                    

Post-emergent Application

Several species of plants were grown in potting soil in disposable styrofoam trays and tomatoes were grown in four-inch pots in the greenhouse. Aqueous spray formulations were prepared and the growing plants were sprayed at a spray volume of 60 gallons per acre and an application rate of 5 lb. per acre. Spray mixtures were prepared in the manner described above. For comparative purposes, plants were also sprayed at 60 gal./acre with a spray mixture containing no growth regulator. Plant injury was again rated according to the schedule disclosed above and observations of growth regulator effects were observed and recorded as follows:

    ______________________________________                                         Effect              Abbreviation in Tables                                     ______________________________________                                         Formative effect on new growth                                                                     F                                                          Epinasty            E                                                          Growth reduction    G                                                          Non-emergence       K                                                          Necrosis            N                                                          ______________________________________                                    

In Table I below there are tabulated various compounds which have been made according to the above illustrative procedures, as well as observations of pre- and post-emergent herbicidal and growth regulator effects.

    TABLE I       EFFECTS ON PLANT SPECIES of Compounds of the formula       ##STR9##       Preemergent Effects Postemergent Effects  Comp'd.      Crab- Cox-      Sugar     Sugar   No. R.sub.n.sup.1 R.sup.2 R.sup.3 Ar M.P. grass comb      Brome Millet Radish beet Millet Alfalfa Oat Radish beet Tomato Comments      on Utility        2431 n = o H H phenyl 180-1° F3G2 F3G2 F3G1 F2G1 F1 F2G1 F2      F3G2 F2 F1 F3G1  F1 Growth reduction                   increased      fruiting 2459 n = o H H 4-CH.sub.3 190°Dec. 0 0 F1 0 0 F2G2 0 F2      0 G1 F2G2 N1 Growth reduction     phenyl 2460 n =       o H H 4-F 180°Dec. F1G1 G1 F1 0 F1 F1G1 0 F1 0 F2 N2F1 0 Growth      reduction     phenyl 2461 n = o H H 3-CH.sub.3 175°Dec. F1G1 G2      F2 F3G3 F2G2 F1G1 0 F3G3 0 F2G1 F2G1 N1 Growth reduction     phenyl              Suppression of foxtail                   and millet 2462 n = o H      H 2-Cl 175°Dec. 0 K3 F1 0 F1 F1 0 N3G3 0 N1F1 F2G2 0 Growth      reduction     phenyl 2654 n = o CH.sub.3 H phenyl 151-3° K4 F3G3      K4 F3G3 F3G3 F3G3 N3G2 N4 N2G2 --  N4 F2 Cotton defoliant.          Promotes tillering of rice,                   oats, wheat. Inhibitor      of                   tasseling. 2757 4-NO.sub.2 H H phenyl 90-2°      F2G2 0 F1G1 F3G3 0 0 0 0 0 0 0 0 Pre-emergent herbicide 2759 5-CH.sub.3      CH.sub.3 H phenyl 102-5° 0 0 0 0 0 0 0 F1 0 0 F1 F1 Post-emergent      growth                   regulant 2769 4-CH.sub.3 H H phenyl 189-92.degre      e. F3G3 F2G2 F2 F2G1 F2G2 F1 F1 F2 F1 F1G1 F2 F3E1 Growth promoter,                   (oats and tomato) 2770 4-CH.sub.3 CH.sub.3 H phenyl      110-15° F3G3 F2G2 F3G2 F3G3 F3G3 F3G2 F1 F3 F1 F1 F2 F3E3      Promotes fruit set on                   tomato. Pre-emergent            herbicide 2791 n = o CH.sub.3 H 3-F ˜65° K4 F3G2 F3G3      F3G3 F3G2 F3G2 G3G3 F3G3 F3G2 F3G2 F3G3 F3G2 Promotes tillering of oats.          phenyl         E1    E3 Pre-emergent herbicide 2792 n = o CH.sub.3 H      4-F ˜55° K4 F3G2 F3G2 F3G3 F3G2 F2G2 F2G2 F3G2 F2 F2G1 F3G2      F3G3 Promotes tillering of     phenyl             E3 oats. Pre-emergent                       herbicide 2797 n =       o CH.sub.3 CH.sub.3 phenyl 175-6° 0 0 0 0 0 F1G1 0 F1 0 0 F2 F2      Growth regulant 2857 n = o CH.sub.2 CH.sub.3 H phenyl ˜60°      K4 K4 F3G3 F3G3 F3G2 F3G3 N2G2 F2G2 F2G2 F1 F2G2 F1G1 Promotes tillering      of                   oats. Pre-emergent                   herbicide 2858      n = o H CH.sub.3 phenyl ˜170°Dec. F2G3 F1G1 F2G1 F2G2 F1G1      F2G2 0 F2G1 0 N1 F2G2 F1 Controls crabgrass                   Growth      regulant 2864 4,7-di Cl CH.sub.3 H phenyl 169-73° 0 G1 0 0 0 G2 0      0 0 0 F2G1 0 Growth regulant 2866 4-F H H phenyl 185-7° F1 0 F1      F1 0 0 0 0 0 F1 F2 F1 Growth regulant 2904 n = o H H 3-F 162-5°      F1 F2G1 K4 F3G2 F2G1 G1 N1 N1F1 N1G1 F2G2 F2G2 0 Combats cheat grass in         phenyl              grain fields. 2906 n =       o H H 3-CF.sub.3 149-152° G1 0 0 0 0 0 0 F1 0 N1G2 F2G2 N1F1      Growth regulant     phenyl 2907 n = o H H 3-Cl 158-61° F2G1 F2G1      F2 F2G1 F1 F1G1 G1 F2G1 0 F1 F2G1 0 Growth regulant     phenyl 2920      4-CH.sub.3 CH.sub.3 CH.sub.3 phenyl 174-75° 0 N2 0 G1 0 0 N1 0 0      0 0 0 Growth regulant 2973 n = o H H 2,4- 196-8° F1G1 F2G1 F2 F1      0 K2 N1 F1G1 0 0 F2G2 0 Growth regulant     dimethyl     phenyl 2974 n =      o H H 3-Cl,-4-CH.sub.3 188-90° F1G1 K2 F2G1 0 0 K2 0 F1 0F1 F1G1      0 Growth regulant     phenyl 2975 n = o H H 3,4-di Cl 185-87° 0      K1 F2 F1G1 0 K2 0 F2 0 F1 F1G1 F1G1 Growth regulant     phenyl 2978 n =      o H H 1-naphthyl 168-71° 0 0 0 0 0 0 0 0 0 F1 F2G1 F1 Growth      regulant 3059 n = o H H 2,5-di- 183-4°       N1 F1 0 N1 0 0      Growth regulant     chloro-     phenyl 3061 n = o H H 4-Br-phenyl      200-2°       0 F3 0 F1 F1 F2 Growth regulant 3112 n = o CH.sub.3      H 2,6- 156-160 0 0 F1 0 0 0 0 0 0 0 F2G1 0     dimethyl-     phenyl 3113      n = o H H adamantyl -- 0 0 0 0 0 0 0 N2 N1 G1 0 N1 3198 n = o CH.sub.3 H      2,3- 100-163 F2G2 F1 F3G1 F3G2 F1 F2G2 0 0 0 0 F2G2 F3     dimethyl-      phenyl 3199 n = o CH.sub.3 H 2,4,5-tri- -- 0 0 0 0 0 0 0 0 0 0 F2G1 0       methyl-     phenyl 3200 n = o CH.sub.3 H 2,5- -- F1 F1 F2 F2G1 F1 F1 0      0 0 0 F2G2 0     dimethyl-     phenyl 3202 n = o benzyl H phenyl -- 0 0      F2 0 0 0 0 F1 0 0 F2G1 F2 3203 n = o CH.sub.3 H tert.butyl 155-158 0 0 0      0 0 0 0 0 0 0 F1 0 3404 n = o CH.sub.3 H 4-nitro- 203-205 F1G1 K2 F3G1      F1G1 F2G2 F2G2 0 F2G2 0 F1 F3 F2     phenyl 3405 n = o CH.sub.3 H      3-chloro-4- 157-160 F1G1 K4 F3G2 F2G2 F3G2 F2G2 N1 F1 0 F1 F2G1 F3      methyl-     phenyl 3406 n = o CH.sub.3 H 3,4- 179-182 F2G2 K4 F3G3 F3G2      F3G3 F3G3 0 0 0 F1G1 F1G1 F2     dimethyl-phenyl 3407 n = o CH.sub.3 H      3,5- 153-156 F2G2 K4 F3G3 F3G2 F3G2 F3G3 0 F2G2 F1 F2G2 F3G1 F2      dimethyl-     phenyl 3197 n = o (CH.sub.2).sub.2 OH H phenyl -- 0 0 0 0      0 0 0 0 0 0 F2 0 3408 n = o CH.sub.3 H 3-ethyl- 74-78 F2G2 K4 K4 F3G3      F3G2 F3G2 0 F2 0 F2G2 F3G2 F3     phenyl 3412 n = o H H 4-chloro-      197-199 F2G1 F2G2 F2G3 F3G2 F2G1 F2G1 0 F3G3 0 F2G2 F3G2 F1     phenyl      3496 4,5,6,7 CH.sub.3 H phenyl >100 0 0 0 0 0 0 0 0 0 0 G1 0  tetrachloro       3626 n = o H H allyl 173-175 F1G1 0 F3G2 G1 0 F2 0 0 0 0 F1 0 3726 n =      o H H 4-methoxy- 197-199 0 0 0 0 0 0 0 F1 0 0 F2 N1     phenyl 3727 n =      o H H 2-methyl-3- 153-155 0 0 0 0 0 0 0 0 0 0 F2 0     chloro-      phenyl 3729 n = o H H 4-isopropyl- 150-152 0 0 0 0 0 0 0 0 0 0 F1 0      phenyl 3730 n = o H H 2-chloro-6- 170-172 0 0 0 0 0 0 0 0 0 0 F1 0      methyl-     phenyl 3810 n = o CH.sub.3 H 4-methoxy- 170-172 0 F2G1 F3G3      F2 F2G2 F2G10 F2G1 F1G1 F2G1 F3G1 F2     phenyl 3811 n = o CH.sub.3 H      2-chloro-4- 66-69 0 0 F2G2 0 F2G1 F1G1 0 F1 0 0 F2G1 F1     methyl-      phenyl 3821 n = o CH.sub.3 H 4-chloro- 169-170 F2G1 K4 K4 F3G2 K4 K4      F2G3 F3G3 F2G2 F3G3 F3G3 F3G1     phenyl 3825 n = o H H 3-benzyl-      158-160 0 0 F1 0 0 0 0 0 0 0 F1 0     oxyphenyl 3826 n = o H H 3-nitro-      184-187 0 0 0 0 0 0 -- F1 0 F1 F1 F1     phenyl 3827 n = o H H 4-benzyl-      194-196 0 0 F1 0 0 0 0 F1 0 0 0 0     oxyphenyl 3828 n =       o H H 4-chloro-3- 181-183 0 0 F1 0 0 0 0 F2 0 F3G2 F1 F1     trifluoro-          methyl-     phenyl 3829 n = o H H 2,4-di- 196-198 F2G2 F3G3 F2G3      F3G2 F2G1 F3G2 F2 F3G2 F2 F3G2 F3G2 F2     chloro-     phenyl 3831 n = o      H H 2-trifluoro- 166-169 0 0 F1 0 F1G1 0 0 F1 0 N1G1 N1G1 N1     methyl-          phenyl 3832 n = o H H 3-chloro- 187-189 0 0 0 0 F1G1 0 0 0 0 F1 F1 0          benzyl 3833 n = o H H 3-methoxyl- 163-165 0 0 F1 0 0 0 0 F3G2 F1      F2G1 F3G1 F1     phenyl 3870 4-fluoro CH.sub.3 H phenyl 45 F2G1 N4 K4      F2G2 F2G2 F2G2 F1G1 F3G3 F1G1 F1G1 F3G3 F3 3948 n = o H H 3,5-di-      188-190 -- -- -- -- -- -- 0 0 0 F1G1 F1 0     methyl-     phenyl 3949 n      = o H H 3-methyl- 70-73       0 0 0 0 F2 0     thiophenyl 3950 n = o H H      2-chloro-4- 187-189       0 F2 G1 0 F2G1 F1     methyl-     phenyl 3954      n = o H H 4-cyano- 230--231       0 0 0 0 F1 F1     phenyl 3955 n = o H      H 4-diethyl- 198-199       0 0 0 0 F1 0     amino-     phenyl 3956 n = o      H H 4-trifluoro- 93-96       F1 F3G3 F1 F3G2 F3G2 F2     methyl-      phenyl 3957 n = o H H 4-chloro-2- 197-199       F1 F3G3 0 F1 F2G1 F2      methyl-     phenyl 3958 n = o H H 4-ethoxy- 189-190       0 0 0 0 F2 F1         phenyl 3959 n = o H H 2-fluoro- 182-184       F1 F1 0 F1 F3G1 F1      phenyl 3960 n =       o H H 3,4-meth- 208-209       0 0 0 0 F1 0     ylenedioxy-     phenyl

The use of many of the growth regulator compounds may be demonstrated by treatment of soybeans (soja max) to increase the number of seeds pods and by treating tomato plants (Lycopersicum esculentum) to increase fruit set. In an illustrative experiment, Soja max (Evans variety) and Lycopersicum esculentum (Tiny Tim variety) were grown in 4-inch pots (one plant per pot) filled with greenhouse potting soil (2 parts good top soil, 11/2 parts builders' sand, 11/2 parts peat, fertilized with 5 lbs. of 12-12-6 fertilizer and 5 lb. of finely ground limestone per cu. yd.). Aqueous spray formulations were prepared and the potted plants were sprayed at a spray volume of 40 gal. per acre and at application rates of 16, 4, 1 and 1/4 oz. per acre. The spray mixtures were prepared by dissolving the proper amount of growth regulator compound in 15 ml. of acetone, adding 2 ml. of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor EL-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 80 ml by addition of a 0.156 wt. percent aqueous solution of liquid non-ionic dispersant (90 wt. percent active trimethylnonyl polyethylene glycol ether, Tergitol TMN-10). Two replicates were sprayed at all application rates. For comparative purposes, plants were also sprayed at 40 gal./acre with water. The number of seed pods and of fruit as percentage of arithmetic mean of the numbers on untreated plants was observed within approximately three weeks after spray treatment and the results are tabulated below. The severity of growth regulatory effect on the plants was estimated on a scale of 0 to 10 and is also recorded in the following table:

    __________________________________________________________________________     GROWTH REGULATING EFFECTS ON TWO SPECIES                                       Soja max         Lycopersicum esculentum                                                        Severity      Severity                                                 Pod Count.sup.○1                                                                of    Fruit Count                                                                            of                                                       Percent in                                                                             Growth                                                                               Percent in                                                                             Growth                                                   Comparison                                                                             Regulat-                                                                             Comparison                                                                             Regulat-                                        Comp'd.                                                                             Rate                                                                               to Untreated                                                                           ing   to Untreated                                                                           ing                                             No.  oz/A.                                                                              Plants  Effect.sup.○2                                                                 Plants  Effect.sup.○2                            __________________________________________________________________________     2431 16  120     2.5   150     0.5                                                  4   105     0     150     0                                                    1   90      0     117     0                                               2459 16  153     7     117     1.5                                                  4   117     1     117     0                                                    1   102     0     150     0                                               2460 16  177     4.5   117     0                                                    4   135     1.5   67      0                                                    1   111     0     100     0                                               2461 16  126     6     67      0.5                                                  4   129     1     133     0                                                    1   105     0     67      0                                               2462 16  109     1.5   254     2                                                    4   92      1     162     0                                                    1   106     0     69      0                                               2654 16  183     9     291     8                                                    4   151     4     255     7.5                                                  1   134     1.5   327     2.5                                             2769 16  95      6.5   162     1                                                    4   102     1     231     0                                                    1   92      0     69      0                                               2770 16  124     7     462     8.5                                                  4   138     2     392     5.5                                                  1   116     1     531     1                                               2791 16  171     9     182     9                                                    4   134     5.5   255     7.5                                                  1   120     2     364     3.5                                             2792 16  131     7.5   300     8                                                    4   141     2     369     5.5                                                  1   127     1     462     2.5                                             2857 16  116     8.5   208     8.5                                                  4   131     2     554     5.5                                                  1   106     1     508     2.5                                             2858 16  102     4     162     0.5                                                  4   106     0.5   69      0                                                    1   106     0     162     0                                               2866 16  109     0     277     0.5                                                  4   95      0     162     0                                                    1   99      0     69      0                                               2904 16  129     2.5   109     0                                                    4   117     0     109     0                                                    1   100     0     73      0                                               2906 16  165     4     117     0.5                                                  4   105     1     133     0                                                    1   96      0     100     0                                               2907 16  138     7     83      2.5                                                  4   111     1.5   150     0                                                    1   87      0     200     0                                               2920 16  102     0     162     0                                                    4   99      0     92      0                                                    1   102     0     115     0                                               2973 16  102     0.5   185     0                                                    4   99      0     162     0                                                    1   109     0     69      0                                               2974 16  123     5.5   50      0.5                                                  4   120     2     100     0                                                    1   96      0     117     0                                               2975 16  132     4     100     1                                                    4   132     0.5   133     0                                                    1   102     0     50      0                                               2978 16  113     1.5   300     0.5                                                  4   92      0     162     0                                                    1   106     0     115     0                                               2982 16  113     1     69      0                                                    4   106     0     115     0                                                    1   109     0     162     0                                               3059 16  117     0     67      0                                                    4   105     0     100     0                                                    1   93      0     100     0                                               3061 16  168     8     100     0.5                                                  4   174     6.5   33      0                                                    1   141     1     117     0                                               3112 16  94      2     66      0.5                                                  4   105     0     75      0                                                    1   101     0     122     0                                               3197 16  105     0     84      0                                                    4   101     0     131     0                                                    1   101     0     75      0                                               3198 16  94      1.5   150     1.5                                                  4   105     0     150     1                                                    1   98      0     94      0                                               3199 16  120     0.5   141     0.5                                                  4   105     0     131     0                                                    1   109     0     66      0                                               3200 16  128     1     131     1.5                                                  4   105     0     75      0                                                    1   109     0     84      0                                               3202 16  101     1     122     0.5                                                  4   98      0     150     0                                                    1   109     0     150     0                                               3404 16  94      2.5   113     8                                                    4   105     0     150     3                                                    1   105     0     122     0                                               3405 16  109     0     103     6                                                    4   98      0     113     1                                                    1   94      0     66      0.5                                             3406 16  101     0.5   103     3.5                                                  4   105     0     84      1                                                    1   94      0     122     0                                               3412 16  129     4     176     1                                                    4   104     1.5   141     0                                                    1   100     0     71      0                                               3821 16  162     8.5   577     8.5                                                  4   155     4.5   438     6.5                                                  1   141     2.5   323     6                                               3829 16  173     5.5   141     5.5                                                  4   154     1.5   159     2                                                    1   128     0     103     0.5                                             __________________________________________________________________________

The information presented in tabular form herein will enable a worker in the art to make a selection from among the growth regulator compounds of the invention and to make some judgment with regard to application rates, depending upon the effect which is desired. It may be seen, for example, that total kills of some species of vegetation may occur at application rates as high as 5 to 10 lb. per acre, whereas beneficial effects may be observed on living plants at application rates of 1 lb. per acre or less.

The growth regulator compounds are usually applied in combination with inert carriers or diluents, as in aqueous sprays, granules and dust formulations in accordance with established practice in the art. An aqueous spray is usually prepared by mixing a wettable powder or emulsifiable concentrate formulation of a growth regulator with a relatively large amount of water to form a dispersion.

Wettable powders comprise intimate, finely divided mixtures of growth regulator compounds, inert solid carriers and surface active agents. The inert solid carrier is usually chosen from among the attapulgite clays, the kaolin clays, the montmorillonite clays, the diatomaceous earths, finely divided silica and purified silicates. Effective surfactants, which have wetting, penetrating and dispersing ability are usually present in a wettable powder formulation in proportions of from 0.5 to about 10 percent by weight. Among the surface active agents commonly used for this purpose are the sulfonated lignins, naphthalenesulfonates and condensed naphthalenesulfonates, alkylbenzenesulfonates, alkyl sulfates and non-ionic surfactants such as products of condensation of ethylene oxide with alkylphenols.

Emulsifiable concentrates of the growth regulator compounds comprise in each instance, a solution of growth regulator compound in a liquid carrier which is a mixture of water-immiscible solvent and surfactants, including emulsifiers. Useful solvents include aromatic hydrocarbon solvents such as the xylenes, alkylnaphthalenes, petroleum distillates, terpene solvents, ether-alcohols and organic ester solvents. Suitable emulsifiers, dispersing and wetting agents may be selected from the same classes of products which are employed in formulating wettable powders.

In general, the growth regulators are applied in formulations which desirably contain from 0.1 percent to 95 percent of a compound of formula (1) and from 0.1 to 75 percent of a carrier or surfactant. However, direct application to plant seeds prior to planting may be accomplished in some instances by mixing powdered solid growth regulator with seed to obtain a substantially uniform coating which is very thin and comprises only one or two percent by weight or less, based on the weight of the seed. In most instances, however, a nonphytotoxic solvent, such as methanol is employed as a carrier to facilitate the uniform distribution of growth regulator on the surface of the seed.

When a compound is to be applied to the soil, as for a pre-emergence application, granular formulations are sometimes more convenient than sprays. A typical granular formation comprises the growth regulator compound dispersed on an inert carrier such as coarsely ground clay, or clay which has been converted to granules by treatment of a rolling bed of the powdered material with a small amount of liquid in a granulating drum. In the usual process for preparing granular formulations, a solution of the active compound is sprayed on the granules while they are being agitated in a suitable mixing apparatus, after which the granules are dried with a current of air during continued agitation. 

We claim:
 1. The method of regulating the growth of plants comprising applying to the plants, the seed or the soil an effective amount of a compound having the structural formula: ##STR10## wherein R¹ is C₁ to C₄ alkyl, nitro or halo and n is zero or an integer from 1 to 4;R² and R³ are H or C₁ to C₄ alkyl, or benzyl; and Ar is adamantyl, C₃ to C₄ alkyl or alkenyl, benzyl, halobenzyl, naphthyl, phenyl or phenyl bearing thereon from one to three of the substituents: cyano, benzyloxy, nitro, bromo, chloro, trifluoromethyl and C₁ to C₄ alkyl, alkenyl, alkoxy, alkylthio and alkyl-substituted amino.
 2. The method of regulating the growth of plants as in claim 1 wherein the set of fruit on crop plants is increased by applying to the foliage of growing plants an effective amount of a compound of claim
 1. 3. The method as in claim 2 wherein the plant is Soja max.
 4. The method as in claim 2 wherein the plant is Lycopersicum esculentum.
 5. A plant growth regulating composition comprising an agriculturally acceptable adjuvant and an effective amount of a compound having the structural formula: ##STR11## wherein R¹ is C₁ to C₄ alkyl, nitro or halo and n is zero or an integer from 1 to 4;R² and R³ are H or C₁ to C₄ alkyl, or benzyl; and Ar is adamantyl, C₃ to C₄ alkyl or alkenyl, benzyl, halobenzyl, naphthyl, phenyl or phenyl bearing thereon from one to three of the substituents: cyano, benzyloxy, nitro, bromo, chloro, trifluoromethyl and C₁ to C₄ alkyl, alkenyl, alkoxy, alkylthio and alkyl-substituted amino. 